It's been one month later and I'm posting another update to give you the status of this case project.
For now I've downsized to Ryzen APU build for my main rig to go even more compact but I will still consider a discrete GPU rig in the future. In the meantime, for this project I will be revising the case structure's design.
First, the side join pieces that run from front to back will be made of thicker aluminum, at least 5mm. This makes screwing side panels easier, and instead of using additional standoffs, which complicates the assembly process. It also means fewer panels- no longer will the top and bottom sides require dual layering. I found it better to use more single layer side with thicker join pieces, than dual layer with thinner join pieces. Fewer pieces overall will need to be cut for each case.
The motherboard tray will be split into two smaller parts for the purpose of making PSU installation easier. I previously had thought of the idea of a tray that slides upwards to insert the PSU, but I thought the locking mechanism to keep it in place would complicate the design too much.
Also I'm moving more of my workflow to Fusion 360 again for the design of the case.
No longer able to make another prototype, I may want to crowdfund it. But that's a situation if push comes to shove.